Un modello di previsione della variazione del body condition score (BCS) nel corso della lattazione in vacche di razza Rendena

Body condition score has been proposed as a practical tool in the management of dairy herds, but guidelines on effective BCS utilization concerned mostly Holstein cows. The present study was aimed to provide general equations of BCS change during lactation in Rendena cows to be used as condition score guidelines in field conditions. Body condition scores (Edmonson et al., 1989) were taken at approximately three-month intervals throughout over 2 years on Rendena cows housed in 24 herds. A total of 6681 records of BCS on 1238 cows were available for statistical analysis. Records were grouped into three parity classes and three classes of mature equivalent milk yield, and were processed through ANOVA according to a time-dependent model. The analysis model accounted for 66% of the variation of test-day BCS. Condition score appeared closely related to linear, quadratic and cubic days in milk (table 2). Body reserves decreased until about 102-118 d from calving and was restored in mid and late lactation. The pattern of change in BCS was similar in cows of different dairy merit (fig. 2), but varied among lactations (fig. 3). Indeed, primiparous cows evidenced a less intense depletion of body reserves in early lactation when compared to multiparous cows, and maximum loss of BCS was -0.25, -0.38 and -0.42 in first, second and third or later lactation cows, respectively. All cows restored body reserves in late lactation, and BCS at 305 days in milk was similar to that at calving (table 4). General equations for computing predicted change in BCS from calving for primiparous and multiparous Rendena cows are provided in table 5. The availability of guidelines of BCS change throughout lactation specific for Rendena cows can improve the effectiveness of this tool in management of herds.